Generally LED lamps in a mobile phone is covered by a light guide plate which may uniformly scatter the point source of light from the LED lamps, when a light ray passed through the light guide plate and reached a keyboard, the transmitted light ray is uniform. However, due to the light guide plate and the keyboard in the conventional mobile phone is separated with each other, and the keyboard is provided with several layers including a key pad, a key and a shading sheet in turn, thus after all components are assembled together, the total thickness of the keyboard is very high.
At present, a kind of light guide key plate has been found in the market, its manufacture process (also called Comolding process) is that firstly forming a light guide plate (usually made from polycarbonate plastic, thus it is also called polycarbonate plastic board, or briefly called PC board) with keyholes by injection moulding, and then placing the light guide plate in a mould for molding silica gel in high temperature and filling the silica gel into the keyholes to form keys. As a result, after sulfurized, the silica gel will be bonded together with the light guide plate, so as to form a light guide key plate. The light guide key plate is advantageous in that the point source of light from LED lamps can be uniformly emitted, because both silica gel and PC are transparent materials, so seen from the front of the keys, the transmitted light rays are uniform. Thus, the light guide key plate may not only play the role of light guide plate, but also be able to realize the functions of key pad. Meanwhile, the overall thickness of the light guide key plate is very low.
Moreover, in this light guide key plate, as shown in FIG. 1, the molded light guide plate 1 is formed with crisscross flow passages 13 between the different keyholes 12 at one side of the molded light guide plate. The flow passages 13 are favorable for uniform dispersing the silica gel during subsequent filling the silica gel into the keyholes so as to lead the surplus silica gel, thus the accumulation of the silica gel can be avoided. However, during the subsequent filling of the silica gel, this structure is unfavorable for the exhaust, and easy to cause that air bubbles exist in the light guide key plate. Moreover, if the silica gel is filled to much, the surplus silica gel will spread onto the surface of product to cause the overflow of silica gel, thus lower the quality of the light guide key plate.